In shuttleless looms, that is, those looms in which weft yarn is supplied from a stationary source location outside the lateral limits of the warp yarns, it is customary to insert each pick of weft by means of a reciprocating inserter or inserters. In the most common shuttleless loom operation a supply of weft is located adjacent the right hand side of the loom and each pick of weft is drawn from the source and inserted into the shed formed between the warp yarns. The insertion itself is effected by means of an inserter carrier which is moved into and from the shed by means of a reciprocating inserter. In this usual form the inserter carrier is met at approximately the center of the warp shed by an extending carrier which grasps the weft being inserted and draws it to the other side of the loom. The extending carrier is moved into and out of the shed by means of a reciprocating inserter in the same manner in which the inserter carrier is moved.
There are two basic weft insertion methods that are used in connection with looms of the type mentioned above. These weft insertion methods are the Gabler and Dewas methods and are frequently referred to as the "hair pin" and "gripper" methods respectively. In the Gabler insertion method a weft yarn end is held clamped outside of the selvedge after cutting and the inserting carrier then pulls a quantity of yarn from the yarn package so that a loop of yarn is initially formed in the warp shed. After a predetermined length of time, the clamped end is releasaed so that the extending carrier can continue to draw the looped yarn to the other side of the loom. By way of contrast the Dewas system utilizes inserting and extending carriers in which the end of the yarn is gripped by the inserting carrier and then this same gripped end is transferred to the extending carrier and drawn on to the other side of the warp.
In the gripper system for inserting weft yarns it is often necessary, or desirable, to be able to insert yarns of different qualities and thicknesses, as it is in the hair pin system. However in the gripper method it is extremely vital that the clamping elements be brought into very accurate, aligned contact so that yarn ends are not lost during a pick and thus result in interruption of loom operation. For example if a loom is working with both a coarse and a fine yarn, that is with yarns of grossly different diameters, it is obvious that a gripper inserter must be able to accommodate and positively grip the yarn of lesser diameter as well as the yarn of larger diameter. Thus it is necessary to result to complex, time consuming and, therefore, expensive machining or other costly manufacturing methods for insuring that extremely close tolerances are obtained between the clamping elements.